Methodology issues in a tailored light treatment for persons with dementia Sleep disturbances are common in persons with Alzheimer's disease or related dementia (ADRD), resulting in significant negative impact on the daytime function of the affected person and on the well-being of caregivers. Past studies have shown that light treatment can help reduce the negative impact of aging on circadian sleep/wake rhythms and thus improve the quality and quantity of sleep in older adults, including those with ADRD. This population would benefit immensely and immediately from a tailored, non- pharmacological treatment to improve sleep efficiency and consolidation. Societal benefits associated with improving sleep quality in older adults can range from reducing the number of falls to increasing cognition and delaying transition of older adults with ADRD to a more controlled living environment. Yet in order to develop a tailored, effective treatment, the circadian light reaching the patient's retina must first be measured and characterized. Current approaches to light therapy for reducing sleep disturbances in older adults do not consider the complete 24-hour light-dark pattern they experience, nor do they integrate light (and dark) treatment into a practical delivery system, thus compromising their therapeutic value. Since the 24-hour light- dark pattern is the primary stimulus for entraining circadian rhythms, it is important to first quantify circadian light exposure throughout the 24-hour day. The light-dark pattern then has to be related to the activity-rest pattern to quantify the degree of entrainment and disruption experienced by an individual. However, standard light meters are of limited use for this task because the spectral sensitivity of the circadian system is very different than that available in commercially available light meters. Moreover, the timing and duration of circadian light exposures must also be measured. The proposed project's aims include: 1) develop field measurement methodologies for obtaining accurate circadian light-dark exposure and activity-rest patterns in those with ADRD using the dime-simeter, a portable, precisely calibrated dime-sized device that continuously records circadian (and visual) light as well as activity for several days or weeks; 2) investigate the acceptance of the dime-simeter by those with ADRD; and 3) implement and test the efficacy of a practical but scientifically sophisticated day-night lighting system designed to improve entrainment to the solar day and improve sleep quality in persons with ADRD and their caregivers. We propose to work with Patricia Higgins, RN, PhD, and Thomas Hornick, MD, from Case Western Reserve University and the Cleveland Veterans Affairs Medical Center, who have the expertise and access to the cohort necessary for conducting the clinical phase of the study. We hope that the dime-simeter can be used as a diagnostic tool for increasing compliance and efficacy of light treatment, thereby improving the quality of life for those with ADRD and for their caregivers.